Mean Platelet Volume (MPV) Does Not Increase After Iron Infusion
MPV levels remain unchanged following iron replacement therapy in patients with iron deficiency anemia, regardless of whether treatment achieves partial or complete response. 1
Key Evidence on MPV Response
The most recent high-quality study directly addressing this question found no change in MPV levels before and after iron treatment in patients with iron deficiency anemia and normal platelet counts 1. Specifically:
- MPV levels remained stable at approximately 8.8-8.9 fL both before and after iron therapy, with no significant difference between partial responders (hemoglobin 10-12 g/dL) and complete responders (hemoglobin >12 g/dL) 1
- This finding held true regardless of the route of iron administration (oral or intravenous) 2
What Actually Changes: Platelet Count and Other Parameters
While MPV remains stable, iron replacement therapy causes significant changes in other platelet parameters:
Platelet Count Decreases
- Platelet count decreases in approximately 72% of patients following iron replacement therapy 2
- Median platelet count drops from 299 × 10⁹/L at baseline to 265 × 10⁹/L at 3 months post-treatment (p < 0.0001) 2
- This decrease occurs even in patients without baseline thrombocytosis 2
Thrombocytosis Resolution
- Thrombocytosis (platelets >400 × 10⁹/L) is present in approximately 22% of iron deficiency anemia patients at baseline 2
- Following iron replacement, thrombocytosis resolves in most patients, with only 5% maintaining elevated counts at 3 months 2
Other Platelet Parameters
- Plateletcrit and platelet distribution width (PDW) decrease following iron therapy 1
- There is an inverse correlation between MPV and platelet count (r = -0.5, p < 0.001), meaning as platelet count decreases with treatment, MPV tends to remain stable or show minimal compensatory changes 1
Clinical Mechanism
The relationship between iron deficiency and platelet parameters is mediated through:
- Serum iron and transferrin saturation are the key iron metabolism parameters affecting platelet count 3
- More severe iron deficiency correlates with higher platelet counts 3
- The mechanism may involve increased erythropoietin production in iron deficiency states, which can stimulate megakaryopoiesis 4
Important Clinical Caveats
Intravenous iron administration may actually decrease platelet counts more than oral iron in some contexts. Data from hemodialysis patients showed platelet counts decreased by 29,000/μL with IV iron versus no change without iron (p = 0.017) 4. This suggests IV iron may have additional effects on platelet production beyond simply correcting iron deficiency.
The absence of MPV change does not mean platelet function is normal. Studies show that platelet aggregation (particularly collagen-induced and ADP-induced) is actually diminished in iron deficiency anemia and improves with treatment 5, even though MPV remains unchanged.
Monitoring Recommendations
When treating iron deficiency anemia:
- Monitor platelet count at 3 months post-treatment, as this is when the most significant changes occur 2
- Do not rely on MPV as a marker of treatment response, as it does not change significantly 1
- Expect platelet count normalization in patients with baseline thrombocytosis within 3 months of adequate iron replacement 2